Cardio

Question 1

Name the 2 important types of cardiac cells and there function.

Answer 1

Electrical cells- specialized cells which conduct electricity. They start and transmit electrical activity in the heart.

Mechanical cells- these cells contract in response to stimuli from the electrical cells.

Question 2

There are 2 types of cardiac MUSCLE cells, name them

Answer 2

Contractile cells ( = working myocardium) and Auto-rhythmic cells (Conducting system)

Question 3

Function of Contractile cells

Answer 3

Produce contractions and generate force.

Question 4

What activates contractile cells?

Answer 4

Change in the membrane potential (just like skeletal muscle)

Question 5

Which cardiac muscle cell makes up 99% of the heart muscle?

Answer 5

Contractile cells

Question 6

State 2 functions of the Auto-rhythmic cells

Answer 6

1. Initiate and distribute electrical activity
2. Controls and coordinates the heart beat but does NOT contribute to contractile force.

Question 7

What are cardiac muscles connected by?

Answer 7

Gap junctions and intercalated disc

Question 7

Function of gap junctions

Answer 7

Allows for the electrical impulse to be transferred from one side to the other

Question 8

Select the best descripton of cardiac muscle cells:
a. not striated, short, unbranched, basal nucleus
b. striated, branched, long, central nucleus
c. short, branched, striated with central nucleus

Answer 8

c

Question 9

Role of desmosomes

Answer 9

Keeps the cardiac cells together ( a disruption of the desmosomes can be fatal)

Question 10

What is needed for calcium to be pumped out of the cell

Answer 10

ATP; therefore it is an ATP dependent process

Question 11

Why is the depolarization phase in cardiac muscles prolonged?

Answer 11

The inflow of calcium results in a prolonged depolarization phase because enough k+ will not leave until all the Ca2+ ions have entered to initiate repolarization.

Question 12

In reference to the shape of the graph what occurs due to the prolonged depolarization?

Answer 12

A plateau is formed

Question 13

What accounts for the slight fall of the plateau?

Answer 13

The plateau falls slightly because there is some leakage of K+ ions during the prolonged depolarization phase but most of the K+ channels remain closed.

Question 14

What is the refractory period

Answer 14

Second stimulus will not evoke a response after the first stimulus no matter how strong

Question 15

State the difference in the refractory periods of skeletal and cardiac muscle. Account for this difference.

Answer 15

The refractory period is short in skeletal muscles but very long in cardiac muscles because depolarization is prolonged which also results in a wider graph for cardiac muscles when compared to skeletal muscles

Question 16

Cardiac muscles CANNOT sum action potentials or contractions and cannot be tetanized true or false?

Answer 16

True

Question 17

At what membrane potential does Na+ channels begin to close in a pacemaker cell?

Answer 17

-40mV

Question 18

Which ion enters the cell after the threshold has been reached

Answer 18

Captain Ca2+

Question 19

What occurs after repolarization in a pacemaker cell

Answer 19

Slow depolarization; there is no break

Question 20

Which node recovers he fastest from refractory period?

Answer 20

Sinoatrial Node

Question 21

Where does the signal from the SA node travel to?

Answer 21

Atrial muscle

Question 22

Which node as the slowest conduction and what is its end location

Answer 22

Atrioventricular node; Ventricle

Question 23

Function of the Atrioventricular Bundle branches

Answer 23

Delays action potential from reaching the ventricles, allowing the atria to empty blood into the ventricles before they contract.

Question 24

Which fibre carries signals throughout the ventricles allowing them to contract?

Answer 24

Purkinje fibres

Question 25

Electrical activity is precisely controlled by: a. Making sure the atria empty into the ventricles before ventricular contraction b. Preventing simultaneous contraction of atria and ventricle c. Ensuring ventricles are relaxed while atria contract d. All of the above

Answer 25

d. All of the above

Question 26

How does the fibrous skeleton facilitate order

Answer 26

It electrically separates atria from ventricles which prevents electrical activity from spreading from atrial muscle to ventricular muscle

Question 27

Why is the SA node known as the pacemaker of the heart?

Answer 27

Because it has the shortest cycle of depolarization and repolarization so it fires quickly and creates the heart rate. Once it fires the impulse travels through the rest of the conducting system rendering the others unable to initiate impulses. This is another way to facilitate order

Question 28

What is the action potential per minute of the SA node, AV node and purkinje fibres respectively

Answer 28

70-80 40-60 20-40

Question 29

List 2 reasons for the slowing of conduction flow at the AV node

Answer 29

1. Diameter of cells at AV node is small. 2. Few gap junctions

Question 30

What is Vagal tone

Answer 30

When vagal influences dominate over sympathetic influences at rest

Question 31

In parasympathetic stimulation AcH binds to muscarinic receptors on nodal membranes resulting in a conductivity increase and decrease in which ions?

Answer 31

Increase conductivity of K+ Decrease conductivity of Ca2+